Presence detector for machine tool control - has piezoelectric sensor, operational amplifier coupled to relay switch, and temp. compensation element

摘要

The detector reacts to the difference in pressure created by the presence of objects in a jet of air. A piezo-resistive sensor (1) which is thermally compensated sends a current directly to an operational amplifier (2). A stable current is applied to the temperature compensation element via a potentiometer (5). The potentiometer is also connected to the operational amplifier so that the op-amp can compare the sensor signal with that set by the potentiometer. The operational amplifier supplies its output signal to a relay switch (4) or optoelectronic coupler. USE - E.g. for control of test or assembly machine in response to arrival of component.